1. Field of the Invention
The invention relates to an apparatus and a method for the adhesive fixing of at least one part, which is to be fixed to a workpiece made from an elastic, resilient and, in particular, material.
2. Prior Art
In the case of elastic, resilient workpieces not directly supportable from the side remote from the joining side against the joining pressure, such as plastic fuel containers produced in the extrusion blowing process and made in particular of higher molecular weight polyethylene, it is difficult to obtain an adequate quality of the connection to the joining part. However, this quality is often of decisive importance, because fuel containers can leak in the joining area. The joining quality is not only dependent on possible deformations of the workpiece during attachment, but also on manufacturing tolerances, which in the case of containers of the aforementioned type are approximately +/-0.5% and therefore very high. Attempts have already been made to compensate these manufacturing tolerances with the aid of a process and an apparatus according to German patent 35 37 670. In this case, prior to the start of a preheating process for plasticizing the workpiece, the position of the joining point is measured in low force manner at the joining point, and as a function of the measured result, the infeeding of a welding unit and the joining part are adjusted via welding stops.
However, no account is taken of the fact that the workpiece, under the pressure of the welding unit and the joining part, resiliently gives way in the vicinity of the joining point and that this does not occur as a parallel displacement, but as a tilting slope, as a function of the position of the joining point. It is also not possible to take account of this deflection as a constant value for similar workpieces, because the deflection is dependent on the wall thickness of the workpiece, manufacturing tolerances, and its ageing state. Less aged workpieces are softer and give way more than more greatly aged workpieces. Thus, the joining quality cannot be improved with the known apparatus and method.